A washing apparatus for cleaning the surface of printing press cylinders usually includes a fresh-cloth supply roller and a dirty-cloth take-up roller for receiving a washing cloth which is impregnated with washing fluid and which is drawn off from the fresh-cloth supply roller and wound up on the dirty-cloth take-up roller. In order to press the washing cloth onto the cylinder, a press-on element, for example a washing roller or a diaphragm part loadable with compressed air, is preferably arranged between the two cloth supply/take-up rollers. The washing cloth is at the same time always to be held under tension, since otherwise it sags, forms loops or can be drawn into the printing machine.
A washing apparatus of this general type is known, for example, from DE 3,005,469 C2. As disclosed here, the winding roller (dirty-cloth take-up roller) draws off the washing cloth from the fresh-cloth supply roller in steps via a ball drive, draft shaft and one-way coupling.
Furthermore, EP 0,479,403 A2 discloses a washing cloth feed which is intended to prevent the washing cloth from folding up or sagging. The washing cloth feed is controlled by means of a spring element and braking device. A helical spring is arranged as a spring element at one end on a sleeve, looping concentrically and frictionally around the fresh-cloth roller shaft, and is fastened at the other end to a fixed support. During the transport of the washing cloth, the spring is stretched a specific amount and thereby prevents the washing cloth from forming folds or from sagging. A brake jaw engages on the shaft of the fresh-cloth roller and controls the cloth feed.
These known prior art devices are disadvantageous in that a large number of components is necessary in order to control the tension and the transport of the washing cloth.